Hydrocarbon conversion

ABSTRACT

A contact material composition of an intimately mixed halogencontaining mixed oxide of at least one cationic species of a naturally occurring Group IIIB element, at least one cationic species of a Group IIA metal of magnesium, calcium, strontium and barium and at least one cationic species of germanium and gallium, as well as methods for hydrocarbon conversion using such contact material compositions are provided.

BACKGROUND OF THE INVENTION

This invention relates generally to the conversion of hydrocarbons and,more specifically, to contact material compositions and oxidativeconversion processes using such compositions.

As the uncertain nature of the limited supplies of and access to crudeoil has become increasingly apparent, alternative sources ofhydrocarbons and fuels have been sought out and explored. The conversionof low molecular weight alkanes (lower alkanes) to higher molecularweight hydrocarbons has received increasing consideration as such lowmolecular weight alkanes may be generally available from more readilysecured and reliable sources. Natural gas, partially as a result of itscomparative abundance, has received a large measure of the attentionthat has focused on sources of low molecular weight alkanes. Largedeposits of natural gas, mainly composed of methane, are found in manylocations throughout the world. In addition, low molecular weightalkanes are generally present in coal deposits and may be formed duringnumerous mining operations, in various petroleum processes, and in theabove- or below-ground gasification or liquefaction of coal, tar sands,oil shale and biomass, for example.

Today, much of the readily accessible natural gas generally has a highvalued use as a fuel whether in residential, commercial or in industrialapplications. Additional natural gas resources, however, are prevalentin many remote regions of the world, such as remote areas of WesternCanada, Africa, Australia, U.S.S.R. and Asia. Commonly, natural gas fromthese remote resources is referred to as "remote natural gas" or, morebriefly, "remote gas."

In many such remote regions, the widespread, direct use of the naturalgas as a fuel is generally not currently profitable. Further, therelative inaccessibility of gas from such resources is a major obstacleto the more effective and extensive use of remote gas as thetransportation of the gas to distant markets wherein the natural gascould find direct use as a fuel is typically economically unattractive.

Of course, while the primary current use of natural gas is as a fuel,natural gas may alternatively be used as a feedstock for chemicalmanufacture. In fact, natural gas is a primary chemical feedstock forthe manufacture of numerous chemicals, such as methanol, ammonia, aceticacid, acetic anhydride, formic acid, and formaldehyde, for example.However, the markets for such chemicals are fairly limited in size.Consequently, methods for converting low molecular weight alkanes, suchas those present in remote natural gas, to higher molecular weighthydrocarbons, preferably, to more easily transportable liquid fuels forwhich the world market is relatively large and/or elastic, are desiredand a number of such methods have been proposed or reported.

Conversion of natural gas to liquid products is a promising solution tothe problem of more effectively and efficiently utilizing low molecularweight hydrocarbons from remote areas and constitutes a specialchallenge to the petrochemical and energy industries. The dominanttechnology currently employed for the utilization of remote natural gasinvolves conversion of the natural gas to a liquid form via theformation of synthesis gas, i.e., a process intermediary composed of amixture of hydrogen and carbon monoxide also commonly referred to as"syngas." In syngas processing, methane, the predominant component ofnatural gas, although typically difficult to activate, is reacted withoxygen or oxygen-containing compounds such as water or carbon dioxide toproduce syngas which in turn is then converted to desired products.

Syngas processing, however, is relatively costly as the production ofsyngas and the subsequent conversion of the syngas are typically verycapital intensive processing schemes. Further, while some of theproducts to which syngas can be converted, such as methanol, mixedalcohols, acetic acid, etc., contain oxygen and are thus logicalproducts for production via syngas processing, hydrocarbon products suchas gasoline and diesel fuel typically do not contain oxygen andconsequently the production of such materials via syngas processingrequires the additional processing step of oxygen removal. Consequently,when such products are produced via syngas processing, the addition andlater removal of oxygen increases the cost of production.

When hydrocarbon products such as gasoline and diesel fuel are sought,the syngas mixture can be converted to syncrude, such as withFischer-Tropsch technology, and then upgraded to the desiredtransportation fuels using typical refining methods. Alternatively,syngas can be converted to liquid oxygenates which can be blended withconventional transportation fuels to form materials such as gasohol,used as an alternative fuel or converted to conventional transportationfuels by catalysts such as certain zeolites.

Because syngas processing typically requires high capital investment,with syngas typically being produced in energy intensive ways such as bysteam reforming where fuel is burned to supply the heat of reforming,and represents an indirect means of higher hydrocarbon production (i.e.,such processing involves the formation and subsequent reaction of thesyngas intermediaries), other means for converting lower alkanesdirectly to higher hydrocarbons have been sought.

Oxidative coupling has been recognized as a promising approach to theproblem of conversion of lower alkanes to higher molecular weighthydrocarbons. The mechanism of action of oxidative coupling processing,however, has not been clearly identified or defined and is not clearlyunderstood. In such oxidative coupling processing, a low molecularweight alkane or a mixture containing low molecular weight alkanes, suchas methane, is contacted with a solid material referred to by variousterms including catalyst, promoter, oxidative synthesizing agent,activator or contact material. In such processing, the methane iscontacted with such a "contact material" and, depending on thecomposition of the contact material, in the presence or absence of freeoxygen gas, is directly converted to ethane, ethylene, higherhydrocarbons and water. Carbon dioxide, the formation of which is highlyfavored thermodynamically, is an undesired product, however, as theformation of carbon dioxide results in both oxygen and carbon beingconsumed without production of the desired higher value C₂₊hydrocarbons.

Catalytic mixtures containing reducible metal oxides are highly activeand many are 100% selective for producing CO₂, that is, they arecombustion catalysts. In order to obtain the desired selectivity forhydrocarbon formation, Group IA metals, particularly lithium and sodium,have been used in such catalytic mixtures. Under the conditions used foroxidative coupling, however, migration and loss of the alkali metalnormally occurs. In order to avoid complete combustion most methods foroxidative conversion have been carried out in the absence of anoxygen-containing gas, relying on the oxygen theoretically beingsupplied by the catalyst.

Nevertheless, in most cases involving oxidative coupling processing ofmethane, carbon monoxide and hydrogen are coproduced in addition todesired C₂₊ hydrocarbons. If desired, such coproduced hydrogen can beused alone, in part or in its entirety, or supplemented with hydrogenfrom another source to effect conversion of carbon oxides to producemethane. Such produced methane can, in turn, be recycled for desiredoxidative coupling processing. Alternatively, the hydrogen can be usedto effect conversion of carbon monoxide to carbon-containing oxygenatessuch as methanol or mixed alcohols (e.g., a mixture of one or morealcohols such as methanol, ethanol, propanols and butanols) or higherhydrocarbons such as a mixture of paraffins and olefins typicallyproduced in the process commonly known as Fischer-Tropsch synthesis.Alternatively or in addition, such coproduced carbon monoxide andhydrogen can, if desired, be combined with olefins, such as thoseproduced during the oxidative coupling processing, to produce variousoxygenates, such as propanol, for example. As described above, however,the production of materials such as oxygenates from carbon monoxide andhydrogen (i.e., synthesis gas) is not a direct approach for theutilization of natural gas, as such processing still involves the use ofthe syngas intermediaries.

Many patents describe processes for converting methane to heavierhydrocarbons in the presence of reducible metal oxide catalysts. Duringsuch processing, the reducible metal oxide "catalyst" typically isreduced and thus most of these patents require or imply the need for aseparate stage to reoxidize the catalyst.

For example, U.S. Pat. No. 4,444,984 discloses a method for synthesizinghydrocarbons wherein methane is contacted with a reducible oxide of tinat an elevated temperature. Such contact results in the tin oxide beingreduced. The reduced composition is then oxidized with molecular oxygento regenerate a reducible oxide of tin.

U.S. Pat. No. 4,495,374 discloses the use of a reducible metal oxidepromoted by an alkaline earth metal in such a method of methaneconversion. During such processing, the reducible metal oxide of thepromoted oxidative synthesizing agent is reduced. The reducedsynthesizing agent can then be removed to a separate zone wherein it iscontacted with an oxygen-containing gas to regenerate the promotedoxidative synthesizing agent.

Examples of other such patents include: U.S. Pat. No. 4,523,049, whichshows a reducible metal oxide catalyst promoted by an alkali or alkalineearth metal, and requires the presence of oxygen during the oxidativecoupling reaction; U.S. Pat. No. 4,656,155, which specifies a reduciblemetal oxide in combination with an oxide of zirconium, an oxide ofyttrium and, optionally, an alkali metal; U.S. Pat. No. 4,450,310, whichis directed to coupling promoted by alkaline earth metal oxides in thetotal absence of molecular oxygen; and U.S. Pat. No. 4,482,644, whichteaches a barium-containing oxygen-deficient catalyst with a perovskitestructure.

Several patents describe catalysts for higher hydrocarbon synthesiswhich can include a Group IIA; a metal of scandium, yttrium orlanthanum; and/or other metal oxides.

Commonly assigned U.S. Pat. No. 4,939,311 discloses a catalystcomposition comprising a mixed oxide of:

a) a Group IIIB metal selected from the group consisting of yttrium,scandium and lanthanum;

b) a Group IIA metal selected from the group consisting of barium,calcium and strontium; and

c) a Group IVA metal selected from the group consisting of tin, lead andgermanium, with the Group IIIB, Group IIA and Group IVA metals in anapproximate mole ratio of 1:0.5-3:2-4, respectively.

U.S. Pat. No. 4,780,449 discloses a catalyst including metal oxides of aGroup IIA metal, a Group IIIA metal, a lanthanide series metal excludingCe, or mixtures thereof. The patent lists as optional promoter materialsmetal oxides of a metal of Groups IA, IIA, IIIA, IVB, VB, IB, thelanthanide series, or mixtures thereof.

Catalysts which contain metal oxides which are reduced under thereaction conditions of use are typically physically and/or chemicallyrelatively unstable under the reaction conditions of use. That is, suchcatalysts generally do not maintain needed or desired physical and/orchemical characteristics for extended periods of time (e.g., suchcharacteristics as reactivity and physical form are typically notmaintained for more than a few minutes) without regeneration,reformation or other remedial procedures.

Also, as the reducible metal oxides of such materials typically undergochemical reduction with use, the activity of the materials for producingdesired products, such as C₂₊ hydrocarbons in the oxidative couplingprocessing of methane, for example, worsen.

One approach for increasing the reactivity of a process utilizing areducible metal oxide contact material has been to use a halogen,particularly chlorine or a compound of chlorine, as a promoter.

U.S. Pat. No. 4,544,784 discloses incorporating a promoting amount of atleast one halogen component in a reducible metal oxide-containingcontact solid. The presence of at least one alkali metal component isdisclosed as prolonging the time period of the retention of the halogenand/or the benefits caused by the presence of the halogen. The enhancedmethane conversion activity and selectivity to higher hydrocarbonsattributable to the halogen component is, however, dissipated over time.Therefore, additional halogen component must be incorporated into thecontact solid as the cycle is repeated in order to maintain thedesirable effects resulting from the contact solid.

U.S. Pat. No. 4,634,800 discloses conducting the contacting of methane,an oxygen-containing gas and a reducible metal oxide in the presence ofat least one promoter of halogen or halogen compound. The promoter maybe incorporated into solids comprising reducible metal oxides prior toconducting the contacting, or, in a preferred form of the invention, thehalogen promoters may be introduced into the process, eitherperiodically or, as preferred, continuously, with the gaseous feedstreams flowing into the process. When halogen-promoted contact solidsare employed in the methane conversion process of the invention, theenhanced methane conversion activity and selectivity to higherhydrocarbons attributable to the halogen component is dissipatedovertime. Therefore, additional halogen component must be incorporatedinto the contact solid. Preferably, a halogen source is at leastperiodically introduced with methane- and oxygen-containing gases duringthe contacting step.

These patents disclose that effective agents for the conversion ofmethane to higher hydrocarbons have previously been found to comprisereducible oxides of metals selected from the group consisting ofmanganese, tin, indium, germanium, antimony, lead, bismuth and mixturesthereof, that reducible oxides of cerium, praseodymium and terbium havealso been found to be useful and that reducible oxides or iron andruthenium are also effective.

These patents acknowledged that the loss of halogen component from thehalogen-containing contact materials results in a reduction in enhancedmethane conversion activity and selectivity to higher hydrocarbons.These patents teach that additional halogen component must beincorporated into the contact solid in order to maintain desirableresults.

In addition, the loss of halide from the contact material can result inthe product effluent being contaminated with halide, necessitatingcostly separation/purification processing.

The search for a stable, long-lived contact material having highactivity and selectivity in the oxidative conversion processing ofhydrocarbons has continued.

SUMMARY OF THE INVENTION

The general object of this invention is to provide an improved contactmaterial composition and an improved method for converting lowermolecular weight alkanes to higher molecular weight hydrocarbons.

It is an object of the present invention to overcome one or more of theproblems described above.

The general object of this invention can be attained, at least in part,through a composition including an intimately mixed halogen-containingmixed oxide which contains:

a) at least one cationic species of a naturally occurring Group IIIBelement;

b) at least one cationic species of a Group IIA metal selected from thegroup consisting of magnesium, calcium, strontium and barium; and

c) at least one cationic species selected from the group consisting ofgermanium and gallium.

As used herein, numerical references to periodic table groups are thoseused by Chemical Abstracts Service as can be found in the CRC Handbookof Chemistry and Physics, published by The Chemical Rubber Co., 1990.

The prior art fails to disclose or suggest a halogen-containing mixedoxide contact material composition of these cationic species. Thecontact materials of the invention result in improved performance suchas through increased C₂₊ selectivity for the conversion of methane tohigher hydrocarbons at oxidative coupling reaction conditions, ascompared to contact materials containing only 2 of these cationicspecies, as well as improved activity maintenance, as compared to priorart compositions containing such halogen.

The invention further comprehends a composition including an intimatelymixed alkaline earth halide-containing mixed oxide containing analkaline earth selected from the group consisting of magnesium, calcium,strontium and barium and a halogen selected from the group consisting offluorine and chlorine, the composition includes:

a) at least one cationic species of a naturally occurring Group IIIBelement selected from the group consisting of yttrium, lanthanum,neodymium, samarium and ytterbium, and

b) at least one cationic species selected from the group consisting ofgermanium and gallium.

The invention still further comprehends a composition including anintimately mixed barium chloride-containing mixed oxide which includes:

a) a cationic species of yttrium, and

b) a cationic species of germanium.

The invention also comprehends methods for the conversion of loweralkanes to higher molecular weight hydrocarbons. In such methods, a feedcomposition including at least one lower alkane species is contactedwith a specified contact material composition. Such contacting is donein the presence of oxygen and at oxidative coupling reaction conditions.

As used herein, the term "reducible" is used to identify those oxides ofmetals which are reduced by contact with C₁ -C₃ alkanes at temperatureswithin the range of about 500° C. to about 1,000° C.

The terms "oxide" and "oxides" include the various oxygen-containingcompositions including hydroxides, carbonates, peroxides, superoxidesand mixtures thereof, for example.

The term "lower alkane" as used herein refers to C₁ -C₃ alkanes.

The term "contact material" as used herein refers to a material whichwhen contacted with a lower alkane and oxygen at oxidative couplingreaction conditions results in the formation of hydrocarbons having ahigher molecular weight than the original feed alkane.

The term "cofeed" operation as used herein refers to that mode ofconversion operation wherein the oxidative coupling contact material issimultaneously contacted by the lower alkane(s) and oxygen (such as inthe form of an oxygen-containing gas). In such operation, the loweralkane(s) and the oxygen can be mixed together before or during theircontact with the contact material.

The term "redox" operation as used herein refers to that mode ofconversion operation wherein the oxidative coupling contact material issequentially contacted by the lower alkane(s), followed by contact withoxygen (such as in the form of an oxygen-containing gas). In suchoperation, the lower alkane(s) and oxygen are generally not mixedtogether to any substantial extent either before or during contact withthe contact material. In some process designs, however, some such"carryover" or inadvertent mixing of the lower alkanes and oxygen mayoccur.

The term "gasoline-type hydrocarbon products" as used herein refers tothose hydrocarbons having a boiling point in the general range of C₄hydrocarbons to about 450° F., inclusive.

The term "substantially free" as used herein to describe the contactmaterial composition generally indicates that the contact materialcomposition excludes amounts of the specified material(s) whichmaterially affect the effectiveness of the contact material in thespecified processing. While the affect of a specified material on theeffectiveness of the contact material will, of course, be dependent onthe material and processing involved, "substantially free" means thatthe contact material composition includes no more than nominal amountsof the specified materials, typically the composition contains an amountof no more than about 1,000 ppm and more specifically the compositioncontains an amount of no more than about 100 ppm and more preferably thecomposition contains an amount of no more than about 50 ppm (0.005 wt.%) of the specified materials.

The terms "intimate mixture" and "intimately mixed" as used herein referto mixing of the different contact material cationic species, eitheralone or in some compound form, on a molecular level. The term isdescriptive of and refers to materials which when thin sectioned toabout 90 nanometers or dispersed on a carbon film and scanned over aspot of no more than about 5 to 10 square microns, preferably a spot ofno more than about 1 to 5 square microns and, more preferably, a spot ofno more than about 0.1 to 1 square micron by way of ScanningTransmission Electron Microscopy with Energy Dispersive X-Ray Analysis(STEM-EDX) exhibits each of the three principal metal cationic speciesof the material in significant amounts (i.e., more than contaminant orimpurity amounts).

Other objects and advantages of the invention will be apparent to thoseskilled in the art from the following detailed description taken inconjunction with the appended claims.

BRIEF DESCRIPTION OF THE DRAWING

The FIGURE is a graphical depiction of the percentage of C₂₊selectivity, O₂ conversion and CH₄ conversion, respectively, versus timeon stream using a contact material according to a typical embodiment ofthe invention.

BRIEF DESCRIPTION OF THE INVENTION

According to the invention, an oxidative coupling contact material and amethod for converting lower alkanes to a higher molecular weighthydrocarbons are provided. The invention contemplates ahalogen-containing mixed oxide oxidative coupling contact materialcomposition and a method of alkane conversion utilizing such contactmaterials composition, generally applicable to alkanes containing from 1to 3 carbon atoms. It is to be understood that while the method can beutilized with higher alkane feedstocks, such use can, as a result ofcompeting reaction kinetics, result in a reduction in the amount ofhigher molecular weight hydrocarbons formed thereby.

In one preferred embodiment of the invention, methane, illustrative ofthe lower molecular weight alkane feedstock useful in the practice ofthe invention, is mixed with air, as a source of oxygen, and theresulting mixture is contacted with a suitable oxidative couplingcontact material, as described below, for the oxidative coupling of theaforesaid alkane. Thus, the invention will be described herein withreference to conversion wherein the lower alkanes converted to highermolecular weight hydrocarbons comprise methane. It is to be understood,however, that feedstocks useful in the practice of the invention willinclude lower alkanes, such as methane, ethane or propane (i.e., C₁ -C₃alkanes) either alone, separately or in mixtures with each other, withor without the presence of other materials, such as inert gases, e.g.,N₂ or minor amounts of other hydrocarbon materials, for example. Naturalgas is an example of a feedstock for use in the practice of at leastsome aspects of the invention. It being understood that natural gas,while containing predominantly methane, can and typically does containat least minor amounts of the other above-identified lower alkanes aswell as other materials such as nitrogen gas and carbon dioxide, forexample.

It is also to be understood that sources or forms of oxygen-containinggas other than air can be used or preferred in the practice of theinvention. Thus, the oxygen-containing gas for use in the method of thisinvention can vary in molecular oxygen content from oxygen-depleted air,to air, to oxygen gas itself, for example. Air or enriched air can be apreferred source of molecular oxygen.

Such oxidative coupling processing of methane, when air is used as asource of oxygen, typically results in a gaseous mixture comprisingethane, and ethylene, illustrative of saturated and unsaturatedaliphatic hydrocarbon products having higher molecular weights than thefeedstock alkanes from which they were formed, and possibly some tracesof aromatics or higher hydrocarbons which may form in the reactor suchas at high operating temperatures, for example, at temperatures greaterthan 750° C., as well as carbon monoxide, carbon dioxide, nitrogen,water and any remaining unreacted feedstock alkane and oxygen. It beingunderstood that conventional catalytic processing schemes such asrefining hydrotreatment, are typically conducted at operatingtemperatures of only about 400° C. to about 450° C.

Such a reaction product mixture may illustratively be used as a chemicalfeedstock or be further reacted, such as occurs during conversion, toform gasoline-type hydrocarbon products. For example, the effluent withdesired or required pretreatment, e.g., H₂ O removal, and/or downstreamhydrotreatment, e.g., N₂ removal, may be passed over a suitablearomatization/oligomerization catalyst, such as a crystallineborosilicate or aluminosilicate molecular sieve material or supportedphosphoric acid, to produce desired gasoline-type hydrocarbon products.Other specific uses of the reactor effluent will be apparent to thoseskilled in the art.

In the above-described embodiment, methane and oxygen (as a part of air)are simultaneously contacted with the oxidative coupling contactmaterial. Such operation is commonly referred to as "cofeed" operationand in such operation, oxygen, which may be needed for the couplingreaction to occur, is also fed to the reactor rather than exclusivelybeing carried into the reactor via the lattice of the contact material,as may be typical of "redox" operation, as described above. Further,cofeed operation may minimize or eliminate the need for subsequentreoxidation of the contact material such as may be required to resupplylattice oxygen to contact materials such as those which typicallycontain reducible metal oxides as typically as required when suchcontact materials are utilized in a redox mode operating scheme.

Generally, a suitable feedstock for the method of this inventioncomprises at least one of methane, ethane and propane and preferablycomprises mostly methane, e.g., at least about 75 percent methane, andmore preferably may be methane as methane is typically the predominanthydrocarbon reserve component which is desired to be converted to ahigher molecular weight hydrocarbon. Thus, a suitable feedstock for themethod of this invention comprises natural gas, gases formed duringmining operations and petroleum processes or in the above-orbelow-ground gasification or liquefaction of coal, tar sands, oil shaleand biomass, for example.

The contacting of the hydrocarbon feedstock with the oxygen-containinggas and in the presence of the contact material is generally performedat oxidative coupling reaction conditions including temperature andpressure. Preferably, such contacting is performed at a temperature inthe range of from about 600° C. to about 1,000° C. and, more preferably,in a range of from about 700° C. to about 900° C. These temperatureranges have been found to be preferred as operation at temperaturesbelow about 600° C. they generally result in the contact material havingrelatively unfavorable product (e.g., C₂₊ hydrocarbons) selectivitieswhile operation at higher temperatures, e.g., temperatures greater thanabout 900° C., can result in generally undesirable thermal reactionsseriously competing with the desired coupling reactions. The productsresulting from such thermal reactions will typically be largelycomprised of H₂, CO_(x) (where x=1 or 2) and may also include coke,acetylene and aromatics such as benzene, for example. Such thermalreactions will typically overwhelm the desired coupling reactions whentemperatures exceed about 1,000° C. It is to be understood, however,that at higher reaction temperatures at least trace amounts of aromaticcompounds may also form.

The contacting of the hydrocarbon feedstock and oxygen with the contactmaterial is preferably performed under a total absolute pressure in therange of from about 0.1 atmosphere to about 10 atmospheres, and morepreferably in the range of from about 1 atmosphere to about 5atmospheres, as operation at pressures exceeding this range typicallyresults in reduced C₂₊ product selectivities while subatmosphericoperation is believed to be economically unattractive as capitalexpenditures escalate rapidly for a system capable of handling theactual volumes of gas required for such an operation to be commerciallypracticed.

The ratio of the partial pressures of the combined feedstock alkanescontaining from 1 to 3 carbon atoms to the oxygen partial pressure atthe entrance of the reactor in the contacting step is preferably in therange of from about 1:1 to about 40:1 and more preferably, in the rangeof from about 2:1 to about 10:1, with ratios in the range of about 2:1to about 5:1 being particularly preferred, as operation at lower C₁ -C₃alkane to oxygen partial pressure ratios generally results in excessivecarbon oxide formation, while operation at higher ratios may result ininsufficient amounts of oxygen being present permit desired levels ofconversion to be attained and consequently results in the remainder ofgreater amounts of unreacted hydrocarbon reacted. The combined partialpressures of the alkanes containing from 1 to 3 carbon atoms in thefeedstock at the entrance to the first reactor (the contacting reactor)is preferably no more than about 10 atmospheres, and, more preferably,no more than about 4 atmospheres. The oxygen partial pressure at theentrance to the first reactor is preferably no more than about 4atmospheres and, more preferably, no more than about 2 atmospheres. Theoxygen partial pressure in the gaseous effluent form the reactor of thecontacting step is preferably substantially 0.

In view of the highly active nature of the subject contact materials forthe oxidative conversion of lower alkanes to a product compositioncontaining higher molecular weight hydrocarbons, the contacting step ispreferably performed at a space velocity of from about 1000 to about1,000,000 volumes total feed gas at ambient conditions per volume ofcatalytic composition per hour and, more preferably at a space velocityof about 50,000 to about 200,000 volumes of total feed gas per volumecatalytic composition per hour, as thermal reactions will generallypredominate this operation at lower space velocities while oxygenconversion will generally be unsuitably incomplete with operation athigher space velocities.

The high activity of the subject contact materials combined with therelease of large amounts of heat associated with the exothermicoxidative coupling reaction of lower alkanes makes heat transfer andtemperature control significant engineering challenges to commercialoperation of the process. Reactors particularly suited for use in thepractice of the invention need to allow for heat transfer and permitdesired temperature control, such reactors include fluidized bedreactors wherein the contact material is finely divided as this promotesa more rapid heat transfer as well as tubular reactors wherein thecontact material is directly applied to the reactor wall to promote heattransfer and to permit desired temperature control.

The present invention provides an intimately mixed contact materialcomposition substantially free of catalytically effective reduciblemetal oxide. In its broader aspects, the halogen-containing mixed oxidecontact material composition of this invention may suitably comprise,consist of, or consist essentially of an intimate mixture containing:

a) at least one cationic species of a naturally occurring Group IIIBelement;

b) at least one cationic species of a Group IIA metal selected from thegroup consisting of magnesium, calcium, strontium and barium; and

c) at least one cationic species of germanium or gallium.

The halogen can be fluorine, chlorine, bromine or iodine. Chlorine isgenerally preferred as chlorine generally results in contact materialswhich in use, for example, in the oxidative conversion of methane orother lower hydrocarbons, particularly lower alkanes to higherhydrocarbons, results in improved performance, e.g., betterselectivities for desired products, such as C₂₊ hydrocarbons in suchconversion processing of methane, as compared to the other named halogenfamily members. In addition, chlorine tends not to volatize as readilyfrom such contact materials as halogen family members such as bromineand iodine.

One theorized explanation for the higher C₂₊ selectivities realized inthe oxidative conversion of methane when using such contact materialswhich contain chlorine, as compared to otherwise similar materials whichcontain some other halogen, is that chlorine, because of its anionicsize, better fits into the active sites of the metal oxide matrix thando such other halogens. Also, the anionic charge density of chlorine, asopposed to that of other halogen family members, could be preferred forsuch contact materials used in the conversion of lower alkanes to highermolecular weight hydrocarbons.

Such compositions will preferably contain about 5 to 20 weight percentof the halogen, on an elemental basis. More preferably, the compositionwill contain about 8 to 17 weight percent of the halogen. For example,compositions of the invention which contain the halogen chlorine willtypically contain chlorine in an amount between about 5 to 20 and,preferably, between about 8 to 17.

In the compositions of the invention, the cationic species of the GroupIIIB element, the Group IIA metal and the germanium or gallium willgenerally be present in an approximate molar or atomic ratio of about 1mole or atom of the Group IIIB element, to no more than about 3 moles oratoms of the Group IIA metal, to no more than about 4 moles or atoms ofgermanium or gallium. Preferably, these cationic species will be presentin a ratio of about 1 mole of the Group IIIB element to about 0.5-3moles of the Group IIA element to about 0.5-4 moles of germanium andgallium and, more preferably, these cationic species will be present ina ratio of about 1 mole of the Group IIIB element to about 0.5-3 molesof the Group IIA element to about 0.5-3 moles of germanium and gallium.In one preferred embodiment, these cationic species will be present inan approximate molar or atomic ratio of 1 (Group IIIB): 1.5-2.5 (GroupIIA): 0.5- 1.5 (germanium or gallium).

In one preferred embodiment of the invention, the Group IIIB element isselected from the group consisting of yttrium, lanthanum, neodymium,samarium and ytterbium, as Group IIIB elements which form oxides that donot have a +4 oxidation state. Our experience has been thataccessibility to a higher oxidation state, e.g., an oxidation state of+4, leads to contact materials which have poorer selectivity and aremore susceptible to reduction, e.g., are susceptible to reduction to a+3 oxidation state, i.e., are reducible metal oxides, and can thus leadto loss of physical strength or lead to increased carbon oxideformation.

In a particularly preferred embodiment, the Group IIIB element isyttrium, at least in part, as a result of its smaller size and itsgeneral commercial availability.

In one embodiment of the invention, the Group IIA metal will be eitherstrontium or barium, as contact materials containing strontium orbarium, as opposed to similar compositions which instead contain otherGroup IIA metals or no Group IIA metals at all, generally exhibit agreater selectivity to higher hydrocarbons when the materials are usedin oxidative coupling of lower alkanes. The greater selectivity of thesubject compositions which contain strontium or barium is believed, atleast in part, to result from strontium and barium having a preferredionic size and basicity, as compared to the other Group IIA metals. Itis believed that the ionic size of strontium and barium, as beinggenerally more similar to Group IIIB metals, facilitates theirincorporation into the material. In addition, basicity is believed tocontribute to the ability of the resulting contact material to performin the hydrocarbon conversion process such as in the ability of thecontact material to abstract hydrogen from the methane molecule as isbelieved is during the oxidative coupling of methane, for example.

One particularly preferred composition of the invention comprises abarium chloride-containing mixed oxide which also comprises a cationicspecies of yttrium and a cationic species of germanium. The inclusion ofa cationic species of germanium is preferred for the contact materialcompositions of the invention as such inclusion generally results in amaterial having improved performance characteristics (e.g., selectivity,activity and/or activity maintenance in oxidative conversion processingsuch as the oxidative coupling of methane), under reaction conditions,germanium does not generally volatize in an amount or to an extentsufficient to materially detrimentally effect the performancecharacteristics of the material.

One such particularly preferred contact material can be represented bythe formula:

    Y(BaCl.sub.2).sub.2 GeO.sub.3.5

The contact materials of the invention can be prepared by any suitablemethod. Several methods of preparation have been used in the preparationof the contact materials of the invention. For example, in one method ofpreparation, yttrium carbonate and barium hydroxide octahydrate aresimply physically mixed with a germanium tetrachloride liquid. As GeCl₄is generally a noxious material, alternative methods of preparation suchas a method wherein yttrium carbonate, barium chloride and germaniumoxide were physically mixed together.

The precursor materials resulting from these preparations will typicallybe calcined at a temperature and duration sufficient to lead to astabilizing interaction among the principal metal cations of thematerial, whereby solid state transformations typically occur and thematerial becomes more homogeneous. For example, the precursors can becalcined at 800° C. for 8 to 12 hours. In such preparations, thecomponents can be characterized as being intermixed on a microscopicscale (e.g., about 100 micron particle size) and with the componentsinteracting to stabilize and form compound(s) containing more than oneof the cationic species.

It is to be understood that exposure to high temperatures (e.g., about700° C. to about 1,000° C. and such as occurs during calcination or,less preferably, in the process use of the material, such as in theoxidative conversion of lower molecular weight alkanes to highermolecular weight hydrocarbons) can and generally will result in desiredstabilizing interaction among the constituents of the material.

Typically, the contact material compositions of the invention will havea surface area generally in the range of about 0.1 m² /gram to about 100m² /gram and preferably will have a surface area in the range of about 1m² /gram to about 10 m² /gram as such compositions having surface areasin this range generally result in better performance in terms ofselectivity and activity, e.g., better C₂₊ selectivity and methaneconversion, in the oxidative conversion of methane to a higher molecularweight hydrocarbon, as compared to similar compositions with a surfacearea outside such ranges.

The subject compositions by being substantially free of catalyticallyeffective reducible metal oxides are not susceptible to over-reductionor over-oxidation and the difficulties associated with such changes, asare those compositions containing reducible metal oxides. With contactmaterials containing reducible metal oxides, the problem ofover-reduction is typically associated with the reduction of the metaloxide to the metal. Often, the selectivity of the contact materialchanges dramatically when the material has been over-reduced, leading tocombustion reactions or the formation of mixtures of carbon oxides withwater and hydrogen when the material is used in the oxidative couplingof lower alkanes such as methane, for example. Some reducible metaloxide-containing contact materials (e.g., tin oxide-containingmaterials) at some conditions (e.g., at high temperature such astemperatures above 850° C. and in the absence of oxygen), onceover-reduced are very difficult to reoxidize and a permanent or nearpermanent alteration in the characteristics of the material occurs, forexample, in the use of the material in the oxidative coupling ofmethane, the alteration can include a loss in selectivity to C₂₊hydrocarbons. In some cases, the reduced metal can react with othermaterials in the composition to form a new phase which is difficult toreoxidize and the contact material is permanently damaged byover-reduction.

In addition, the subject contact material compositions are sufficientlyhard so that they can be used to form a material that can be fluidizedwithout large losses of material in the form of powdery materials,frequently referred to as "fines." In fluid bed operation, fines arefrequently carried out with the vapors from the reactor. Additionally,the fines are generally not easily separated from the product gases incommon separating devices such as cyclones. Thus, costly separationtechniques are required to effect separation of the fines from theproduct gases. The loss of contact material in the form of fines alsonecessitates the addition of more contact material to the process toreplace that which has been lost and thereby increases the cost of suchprocessing.

Contact materials containing metal oxides which are reducible under thereaction conditions of use typically are relatively soft materials whichexperience breaking apart during use. The softness is, in part, due tochanges in the material during oxidation and reduction. Frequently, thematerial in its various oxidation states has very different densities,e.g., the material contracts and swells as it is reduced and oxidized.The smaller particles or powders resulting when the material undergoesphysical degradation results in pressure drop buildups (in fixed bedoperation) and leads to loss of contact material (in fluid bedoperation).

The contact materials and the processes utilizing the subject contactmaterials illustratively disclosed herein can suitably be practiced inthe absence of any component or ingredient or process step,respectively, which is not specifically disclosed herein.

Characterization of the contact material using XRD, XPS and electronmicroscopy has shown some novel features of this contact material. Abarium species with a higher 3d binding energy than those reported inthe literature has been observed by XPS in the fresh catalyst. Thisbinding energy of 781.6 eV can be attributed to a barium oxychloride.Also there is evidence of an oxychloride present in the fresh catalystbased on chlorine XPS binding energies of 199.9 eV. The barium 3dtransition changes with long exposure to X-rays. These high bindingenergies do not exist in the used contact material, e.g., in theconversion of lower alkanes to higher hydrocarbons, a contact materialis generally considered "used" after being exposed to lower alkanes andoxygen at oxidative coupling reaction conditions for several hours(typically more than 2 hours). See Table 1.

The present invention is described in further detail in connection withthe following examples which illustrate various aspects involved in thepractice of the invention. It is to be understood that all changes thatcome within the spirit of the invention are desired to be protected andthus the invention is not to be construed as limited by these examples.

EXAMPLES EXAMPLE 1

Synthesis of Y(BaCl₂)₂ Ge₃ O_(y), where y=a molar amount necessary forthe contact material to be at stoichiometric balance, for the nominalcomposition, y=7.5.

A physical mixture having the nominal composition Y(BaCl₂)₂ Ge₃ O_(y)was prepared by physically mixing a yttrium carbonate (Y₂ (CO₃)₃. 3H₂ O,6.2 gm, 0.015 moles) and barium hydroxide octahydrate (Ba(OH)₂.8H₂ O,19.1 gm, 0.061 moles). Germanium chloride (GeCl₄, 19.3 gm, 0.09 moles)was added dropwise to this physical mixture in air to form a slurry. Theresulting slurry was mixed via mortar and pestle resulting in a materialhaving a paste consistency. The paste, which was white in color, wastransferred to a crucible and then calcined in air as follows: Thesample was heated at the rate of 4° C./min to 800° C. and was thenmaintained at that temperature for 5 hours. X-ray diffraction (XRD) ofthe calcined material showed several crystalline phases including BaGe₄O₉ and other unidentified phases.

EXAMPLE 2

Synthesis of Y(BaCl₂)₂ GeO_(y), where y=a molar amount necessary for thecontact material to be at stoichiometric balance, for the nominalcomposition, y=3.5.

A preparation having the nominal composition Y(BaCl₂)₂ GeO_(y) wasprepared by:

Weighing barium hydroxide octahydrate (Ba(OH)₂.8H₂ O, 32.19 gm, 0.102moles) and yttrium carbonate (Y₂ (CO₃)₃.3H₂ O, 10.31 gm, 0.025 moles)into a mortar and pestle and grinding them together for several minutes.The mixture was then transferred to a nitrogen filled glove bag where10.83 gm 0.0505 moles of germanium chloride (GeCl₄) was added dropwise.Mixing these precursors together created a paste that emitted some HClfumes. The paste was then transferred to a yttria stabilized zirconiacrucible for calcination in air. Calcination was as follows: Thematerial was heated at a rate of 4° C./min to 400° C., maintained atthat temperature for 60 minutes before heating at a rate of 2° C./min to800° C. where it was maintained for 720 minutes. The sample was thencooled. The major crystalline phase was BaCl₂ and BaCl₂. H₂ O, with apreviously undisclosed phase of Ba₅ Cl₆ GeO₄. Minor phases of BaGe₂ O₅and Y (OH)₃ also were present. The unit cell parameters for the Y₂ GeO₅solid solution are a=10.4329(75) Å, b=6.7763(26) Å, c=13.0262 (158) Å.The surface area of the fresh contact material was 2.6 m² /gm.

EXAMPLE 3

An alternative method of preparation of the Y(BaCl₂)₂ GeO_(y), wherey=3.5 contact material was used and involved physically mixing in airyttrium carbonate (Y₂ (CO₃)₃.3H₂ O, 20.61 gm, 0.05 moles) with bariumchloride (BaCl₂.H₂ O, 48.91 gm, 0.20 moles), and germanium oxide GeO₂,10.47 gm, 0.10 moles) using a mortar and pestle. After the precursorswere ground to a homogeneous white powder the mixture was transferred toa yttria stabilized zirconia crucible for calcination. Calcination wasas follows: The sample was heated at a rate of 4° C./min to 400° C.,then maintained at that temperature for 60 minutes before increasing thecalcination at a rate of 2° C. until a temperature of 850° C. wasattained. The material was maintained at 850° C. for 6 hours. The samplewas then cooled ballistically as the oven cooled. XRD analysis showedthere were seven identifiable phases, BaCl₂.2H.sub. 2 O, BaGe₄ O₉, andY₂ O₃ were all major phases. Intermediate phases were GeO₂, Y₂ Ge₂ O₇,and BaCl₂. XPS analysis indicates a high binding energy peak for bariumat around 783 eV binding energy.

EXAMPLE 4

Preparation of a contact material having the nominal composition ofY(BaCl₂)₂ GaO_(y), where y=a molar amount necessary for the contactmaterial to be at stoichiometric balance, for the nominal composition,y=3.

Yttrium carbonate (Y₂ (CO₃)₃.3H₂ O, 8.26 gm, 0.020 moles), bariumchloride (BaCl₂.2H₂ O, 19.74 gm, 0.08 moles), and gallium nitrate(Ga(NO₃)₃. 9H₂ O, 10.24 gm, 0.040 moles) were physically mixed in airusing a mortar and pestle. After the precursors were ground to a moistpaste the mixture was transferred to a yttria stabilized zirconiacrucible for calcination. Calcination was as follows: The sample washeated at a rate of 4° C./min to 400° C., then maintained at thattemperature for 60 minutes before increasing the temperature at a rateof 2° C./min to 850° C., and then maintained at that temperature for 720minutes. The sample was then cooled ballistically as the oven cooled.

EXAMPLE 5

Preparation of a contact material having the nominal compositionY(BaBr₂)₂ GeO_(y), where y=a molar amount necessary for the contactmaterial to be at stoichiometric balance, for the nominal composition,y=3.5.

Yttrium carbonate (Y₂ (CO₃)₃.3H₂ O, 6.18 gm, 0.015 moles), bariumbromide (BaBr₂, 17.83 gm, 0.06 moles), and germanium oxide (GeO₂, 3.14gm, 0.03 moles) were physically mixed in air using a mortar and pestle.After the precursors were ground to a moist paste the mixture wastransferred to a yttria stabilized zirconia crucible for calcination.Calcination was as follows: The sample was heated at a rate of 4° C./minto 400° C., then maintained at that temperature for 60 minutes beforeincreasing the temperature at a rate of 2° C./min to 850° C., and thenmaintained at that temperature for 800 minutes. The sample was thencooled ballistically as the oven cooled.

EXAMPLES 6-10 Catalytic Activity for Methane Oxidative Coupling Examples

The contact materials of Examples 1-5, respectively, were tested forcatalytic activity. Feed mixtures were from premixed tanks containingeither a feed mixture having a targeted methane to oxygen mole ratio of2 to 1 and comprising 7% O₂, 14% CH₄ and the balance of N₂, or a feedmixture having a targeted methane to oxygen mole ratio of 5 to 1 andcomprising 6% O₂, 30% CH₄ with the balance of nitrogen. The contactmaterials were crushed and sieved 80/120 (e.g., particles pass through80 mesh screen but are retained on 120 mesh screen), and mixed with anappropriate amount of alpha alumina diluent that was 30/50 mesh toresult in a material just providing about 100% O₂ conversion. Many ofthese contact materials required no alumina diluent since they were notvery active compared to their nonhalide-containing counterparts.

The Table below identifies actual methane to oxygen ratio of the feedmixture used in each of these Examples and the ratio of contact materialto diluent (CM/D) in those Examples where diluent was used.

    ______________________________________                                                Contact Material                                                                           Feed Mixture (actual                                     Example of Example   CH.sub.4 /O.sub.2 Mole Ratio)                                                                CM/D                                      ______________________________________                                        6       1            5.236          4.42/2.3                                  7       2            5.242          2.23/1.2                                  8       3            1.941          3.79/2.0                                  9       4            4.828          NONE                                      10      5            4.466          NONE                                      ______________________________________                                    

The gas flows were controlled by Brooks mass flow controllers which werecontrolled by a SETCON program. In fact, the entire reactor system wasautomated by using SETCON to control all reactor heating cycles, gasflows, gas chromatograph injections, and valve switching. Productanalysis was done using an H.P. 5890 gas chromatograph in a multiplecolumn configuration. Multichrome was used for integration of the G.C.peaks and a 1032 database for a conversion, selectivity, and massbalance calculations. The results are given in Tables 1-5, respectively,below.

                  TABLE 1                                                         ______________________________________                                        REACTION CONDITIONS                                                           Hours into                                                                             9:20      10:36     11:52   13:08                                    run                                                                           Temp. C. 800.0     799.9     850.1   850.0                                    (Avg.)                                                                        SV (1/hr.)                                                                             5.35E + 03                                                                              7.12E + 03                                                                              5.35E + 03                                                                            7.12E + 03                               O.sub.2 conv.,                                                                         54.403    42.131    93.256  99.254                                   mole %                                                                        CH.sub.4 conv.                                                                         16.35     13.66     24.04   16.64                                    mole %(1)                                                                     CH.sub.4 conv.                                                                         15.23     12.95     22.25   15.06                                    mole %(2)                                                                     Res. time                                                                              0.068     0.052     0.065   0.049                                    (sec.)                                                                        SELECTIVITIES, mole %                                                         CO       12.63     10.97     16.29   28.82                                    CO.sub.2 9.30      8.15      13.57   54.37                                    C.sub.2 H.sub.4                                                                        49.47     46.57     52.34   13.29                                    C.sub.2 H.sub.6                                                                        22.74     29.11     10.06   1.11                                     C.sub.2 H.sub.2                                                                        0.00      0.00      1.77    1.11                                     C.sub.3 H.sub.8                                                                        0.51      0.69      0.00    0.00                                     C.sub.3 H.sub.6                                                                        4.57      3.96      5.70    1.30                                     C.sub.4 's                                                                             0.78      0.55      0.25    0.00                                     C.sub.2+ 78.07     80.89     70.13   16.81                                    C.sub.2 H.sub.4 /C.sub.2 H.sub.6                                                       2.17      1.60      5.20    11.99                                    H.sub.2 /CO                                                                            0.00      0.00      0.00    0.00                                     CO/CO.sub.2                                                                            1.36      1.35      1.20    0.53                                     ______________________________________                                          (1)CH.sub.4 conversion calculated from CH.sub.4 in minus CH.sub.4 out.       (2)CH.sub.4 conversion calculated from carbon in products.               

                                      TABLE 2                                     __________________________________________________________________________    REACTION CONDITIONS                                                           Hours into run                                                                           13:22 14:22 15:23 16:24 17:24 18:25                                Temp. C. (Avg.)                                                                          799.9 800.1 799.7 799.7 850.0 850.0                                SV (1/hr.) 3.15E + 03                                                                          3.15E + 03                                                                          315E + 03                                                                           315E + 03                                                                           315E + 03                                                                           315E + 03                            O.sub.2 conv., mole %                                                                    76.749                                                                              77.360                                                                              77.860                                                                              78.367                                                                              99.107                                                                              98.795                               CH.sub.4 conv. mole %(1)                                                                 20.92 21.33 21.47 21.50 25.22 25.13                                CH.sub.4 conv. mole %(2)                                                                 20.00 20.22 20.28 20.52 22.97 23.01                                Res. time (sec.)                                                                         0.116 0.116 0.116 0.116 0.111 0.111                                SELECTIVITIES, mole %                                                         CO         13.02 11.83 11.66 12.16 5.83  6.58                                 CO.sub.2   13.35 13.42 13.53 13.28 20.10 20.27                                C.sub.2 H.sub.4                                                                          50.38 50.91 50.73 50.84 55.89 54.89                                C.sub.2 H.sub.6                                                                          17.04 17.41 17.56 17.31 9.99  10.14                                C.sub.2 H.sub.2                                                                          0.38  0.50  0.48  0.38  1.83  1.84                                 C.sub.3 H.sub.8                                                                          0.41  0.42  0.41  0.41  0.00  0.00                                 C.sub.3 H.sub.6                                                                          4.43  4.48  4.55  4.54  5.93  5.86                                 C.sub.4 's 0.99  1.03  1.07  1.08  0.43  0.41                                 C.sub.2+   73.63 74.76 74.80 74.55 74.07 73.14                                C.sub.2 H.sub.4 /C.sub.2 H.sub.6                                                         2.96  2.92  2.89  2.94  5.60  5.41                                 H.sub.2 /CO                                                                              0.00  0.00  0.00  0.00  0.00  0.00                                 CO/CO.sub.2                                                                              0.97  0.88  0.86  0.92  0.29  0.32                                 __________________________________________________________________________     (1)CH.sub.4 conversion calculated from CH.sub.4 in minus CH.sub.4 out.        (2)CH.sub.4 conversion calculated from carbon in products.               

                  TABLE 3                                                         ______________________________________                                        REACTION CONDITIONS                                                           Hours into                                                                             11:46     13:28     15:09   16:50                                    run                                                                           Temp. C. 899.7     799.8     849.9   850.1                                    (Avg.)                                                                        Flow Rate                                                                              149.1     149.3     149.3   99.4                                     (g/hr.)                                                                       SV (1/hr.)                                                                             2.98E + 03                                                                              2.99E + 03                                                                              2.99E + 03                                                                            1.99E + 03                               WHSV     2.13E + 03                                                                              2.14E + 03                                                                              2.14E + 03                                                                            1.42E + 03                               (1/hr.)                                                                       O.sub.2 conv.,                                                                         66.728    62.627    98.304  99.496                                   mole %                                                                        CH.sub.4 conv.                                                                         36.25     35.54     48.29   46.58                                    mole %(1)                                                                     CH.sub.4 conv.                                                                         35.94     34.37     47.58   45.88                                    mole %(2)                                                                     Res. time                                                                              0.123     0.123     0.117   0.176                                    (sec.)                                                                        SELECTIVITIES, mole %                                                         CO       18.43     19.36     13.02   7.29                                     CO.sub.2 20.96     18.70     28.80   35.74                                    C.sub.2 H.sub.4                                                                        44.44     45.00     42.98   41.73                                    C.sub.2 H.sub.6                                                                        10.63     11.90     4.91    4.76                                     C.sub.2 H.sub.2                                                                        0.55      0.37      2.01    1.88                                     C.sub.3 H.sub.8                                                                        0.32      0.38      0.00    0.00                                     C.sub.3 H.sub.6                                                                        3.10      3.15      3.48    3.50                                     Methyl acetylene                                                                       0.18      0.13      0.71    0.81                                     ALLENE   0.00      0.00      0.34    0.36                                     C.sub.4 's                                                                             0.00      1.01      2.40    2.33                                     C.sub.2+ 60.27     61.12     55.41   53.80                                    C.sub.5+ 0.16      0.00      1.34    1.61                                     Olefin ratio                                                                           4.47      3.96      10.09   10.15                                    C.sub.2 H.sub.4 /C.sub.2 H.sub.6                                                       4.18      3.78      8.76    8.76                                     H.sub.2 /CO                                                                            0.00      0.00      0.00    0.00                                     CO/CO.sub.2                                                                            0.88      1.04      0.45    0.20                                     ______________________________________                                         (1)CH.sub.4 conversion calculated from CH.sub.4 in minus CH.sub.4 out.        (2)CH.sub.4 conversion calculated from carbon in products.               

                  TABLE 4                                                         ______________________________________                                        REACTION CONDITIONS                                                           Hours into                                                                             12:17     13:59     15:40   17:21                                    run                                                                           Temp. C. 800.1     800.0     844.0   849.3                                    (Avg.)                                                                        Flow Rate                                                                              301.5     152.3     301.5   152.3                                    (ml/min.)                                                                     SV (1/hr.)                                                                             4.52E + 03                                                                              2.29E + 03                                                                              4.52E + 03                                                                            2.29E + 03                               WHSV     4.07E + 03                                                                              2.05E + 03                                                                              4.07E + 03                                                                            2.05E + 03                               (1/hr.)                                                                       O.sub.2 conv.,                                                                         30.397    72.404    78.543  98.566                                   mole %                                                                        CH.sub.4 conv.                                                                         11.57     20.08     21.88   23.49                                    mole %(1)                                                                     CH.sub.4 conv.                                                                         11.51     20.01     21.76   23.38                                    mole %(2)                                                                     Res. time                                                                              0.081     0.160     0.078   0.153                                    (sec.)                                                                        SELECTIVES, mole %                                                            CO       7.51      7.98      7.82    3.58                                     CO.sub.2 11.38     21.11     20.92   29.20                                    C.sub.2 H.sub.4                                                                        36.55     44.38     45.53   45.37                                    C.sub.2 H.sub.6                                                                        40.82     21.02     19.69   12.57                                    C.sub.2 H.sub.2                                                                        0.00      0.22      0.52    1.24                                     C.sub.3 H.sub.8                                                                        0.95      0.52      0.36    0.00                                     C.sub.3 H.sub.6                                                                        2.44      3.75      3.87    4.73                                     Methyl acetylene                                                                       0.00      0.12      0.26    0.74                                     ALLENE   0.00      0.06      0.14    0.33                                     C.sub.4 's                                                                             0.00      0.85      0.89    1.69                                     C.sub.2+ 81.11     70.21     70.25   65.60                                    C.sub.5+ 0.00      0.00      0.00    0.55                                     Olefin ratio                                                                           0.94      2.26      2.50    4.13                                     C.sub.2 H.sub.4 /C.sub.2 H.sub.6                                                       0.90      2.11      2.31    3.61                                     H.sub.2 /CO                                                                            0.00      0.00      0.00    0.00                                     CO/CO.sub.2                                                                            0.66      0.38      0.37    0.12                                     ______________________________________                                         (1)CH.sub.4 conversion calculated from CH.sub.4 in minus CH.sub.4 out.        (2)CH.sub.4 conversion calculated from carbon in products.               

                  TABLE 5                                                         ______________________________________                                        REACTION CONDITIONS                                                           Hours into                                                                             11:54     13:35     15:16   16:58                                    run                                                                           Temp. C. 800.0     799.8     847.7   849.0                                    (Avg.)                                                                        Flow Rate                                                                              299.8     150.1     299.8   149.9                                    (ml/min.)                                                                     SV (1/hr.)                                                                             4.50E + 03                                                                              2.25E + 03                                                                              4.50E + 03                                                                            2.25E + 03                               WHSV     4.12E + 03                                                                              2.06E + 03                                                                              4.12E + 03                                                                            2.06E + 03                               (1/hr.)                                                                       O.sub.2 conv.,                                                                         45.523    68.970    71.150  88.345                                   mole %                                                                        CH.sub.4 conv.                                                                         14.15     18.31     19.68   21.81                                    mole %(1)                                                                     CH.sub.4 conv.                                                                         14.66     18.58     19.86   21.85                                    mole %(2)                                                                     Res. time                                                                              0.082     0.163     0.078   0.156                                    (sec.)                                                                        SELECTIVES, mole %                                                            CO       19.98     24.83     22.12   20.78                                    CO.sub.2 10.52     14.53     12.63   17.70                                    C.sub.2 H.sub.4                                                                        51.09     48.16     51.03   46.50                                    C.sub.2 H.sub.6                                                                        13.73     6.63      7.15    4.48                                     C.sub.2 H.sub.2                                                                        0.00      0.78      0.88    1.77                                     C.sub.3 H.sub.8                                                                        0.00      0.00      0.00    0.00                                     C.sub.3 H.sub.6                                                                        1.67      1.60      2.19    2.83                                     Methyl acetylene                                                                       0.00      0.08      0.21    0.47                                     ALLENE   0.00      0.06      0.09    0.21                                     C.sub.4 's                                                                             2.50      2.05      2.34    2.31                                     C.sub.2+ 68.98     59.21     63.59   57.89                                    C.sub.5+ 0.52      1.35      1.35    2.95                                     Olefin ratio                                                                           4.03      7.82      7.64    10.88                                    C.sub.2 H.sub.4 /C.sub.2 H.sub.6                                                       3.72      7.26      7.14    10.39                                    H.sub.2 /CO                                                                            1.90      1.71      1.75    1.17                                     CO/CO.sub.2                                                                            1.90      1.71      1.75    1.17                                     ______________________________________                                         (1)CH.sub.4 conversion calculated from CH.sub.4 in minus CH.sub.4 out.        (2)CH.sub.4 conversion calculated from carbvon in products.              

Discussion of Results

Relative feed rates varied with the activity of the contact material butfell in the range of 2,000 to 50,000 standard cc per hour per cc.contact material. The activity and selectivity for C₂₊ hydrocarbons ofcontact materials of Examples 1-5 at various flow rates and temperaturescan be seen in Tables 1-5. Contact materials that had higher amounts ofalumina diluent had lower C₂₊ selectivities since the alumina's aciditycontributes to the combustion activity. With these less active contactmaterials the activity due to the alumina becomes more significant. Thebest C₂₊ yields of 25%-27% came from the YBa₂ GeO_(y) (Cl) run withlittle or no alumina dilution and a feed ratio of CH₄ /O₂ =2:1.Olefin/paraffin ratios are in the range of 5-10 for the Y/Ba/Ge samplesand were lower when the Ge was replaced with Ga.

EXAMPLES 11-14

Contact material of Example 1 was examined in a series of experiments.The contact material screened to 40/60 mesh and 0.25 gm was mixed with1.5 gms of 40/60 mesh Vycor glass. The mix was loaded in a 8 mm (insidediameter) quarts tube with a 3 mm (o.d.) quartz thermowell along thecenter line of the tube. The bed length was about 3.5 cm. Space aboveand below the bed was filled with 14/20 mesh quartz.

The reactor tube was placed in a 15 cm single-zone furnace. An externalgas recycle pump was connected to the end couplings. Feed gases werepreblended and compositions given are vendor analyses (Matheson).Ultrapure gases were used in all experiments.

EXAMPLE 11

Replicate, on-line, gas chromatographic analyses of the feed gas wereobtained during the first 4 hours. A nominal 2:1 CH₄ /O₂ feed gas blendwas used. Analyzed values were 14.72% CH₄, 7.47% O₂, balance N₂. Thereactor was heated rapidly to temperature and GC samples taken aboutevery hour. Water was adsorbed on calcium sulfate prior to analysis.GC#'s and Temperatures are as follows:

    ______________________________________                                        GC        Temp. (°C.)                                                                       Fresh Feed Rate (sccm)                                   ______________________________________                                        5-9       750        100                                                      10-12     700        100                                                      13-15     650        100                                                      16-18     600        100                                                      19-20     750        100                                                      ______________________________________                                    

Discussion of Results

Conversions, even at 750° C., were very low. At such low conversions,very little product is made and the relative uncertainties, just due touncertainties in measurements, are large. At 750° C., methane conversionwas about 3% and the selectivity to C₂₊ hydrocarbons was about 75%.Selectivity to CO and CO₂ were about equal at 12%-13% each.

EXAMPLE 12

Due to the low conversion of methane realized in Example 11, the feedrate was reduced to 10 sccm--10% of that used in Example 11. A gasrecycle rate of about 90 sccm was also used to reduce thermal reactionswhich might begin at such a low fresh feed rate. The same contactmaterial bed was kept from the previous example.

Discussion of Results

At 750° C., the C₂₊ selectivity was 48% with methane conversion of about23%. Selectivity to CO was about 18% and to CO₂ was about 35%.

EXAMPLE 13

Testing was continued with the same loading of contact material as inExample 12. Conditions were fixed at 750° C., fresh feed of 5 sccm, andrecycle gas at about 100 ccm. Eight GC samples were taken over about 8hours.

Discussion of Results

These results shows a slightly higher conversion of methane due to thelower feed rate but essentially the same selectivities for C₂₊hydrocarbons as the 750° C. conditions of Example 12.

EXAMPLE 14

The same loading of contact material as used in Example 13 was used buta different feed gas feed was used. Analyzed composition of the new feedgas was 23.87% CH₄, 5.13% O₂, balance N₂ --a nominal 5:1 methane tooxygen ratio. Cool product gas recycle was kept at 100 ccm and the feedrate and temperature was varied as follows:

    ______________________________________                                        GC        Temp. (°C.)                                                                       Fresh Feed Rate (sccm)                                   ______________________________________                                        1-4       750        5                                                        5-7       800        5                                                         8-15     800        10                                                       ______________________________________                                    

At the end of this run, the contact material was unloaded. The usedcontact material was white and free flowing. The fresh contact materialwas also white. Thus the contact material did not coke as determined byvisual inspection.

EXAMPLE 15 ACTIVITY MAINTENANCE

The contact material of Example 3 was sieved to 40-60 mesh and a 2.0 gmportion was loaded in a quartz tube. The loaded quartz tube was placedin a three zone electric tube furnace.

The material was tested, at 850° C., for the oxidative conversion ofmethane to higher hydrocarbons for a period of time on stream of 1300hours. In this testing a feed gas blend of 40% CH₄, 4% O₂, and balanceN₂ was passed over the contact material sample at a feed rate of 150standard cubic centimeters per minute (sccm).

Oxygen conversion, methane conversion, and C₂₊ selectivities (each interms of percents) versus total time on stream are shown in the Figure.

Discussion of Results

As can be seen in the Figure, both methane conversion and C₂₊selectivity were fairly constant over the entire test time on stream.These results show a high degree of activity maintenance for the testedmaterial.

The foregoing detailed description is given for clearness ofunderstanding only, and no unnecessary limitations are to be understoodtherefrom, as modifications within the scope of the invention will beobvious to those skilled in the art.

That which is claimed is:
 1. A method for converting lower alkanes to aproduct composition comprising a higher molecular weight hydrocarbon,said method comprising contacting a feed composition comprising at leastone lower alkane material with an intimately mixed halogen-containingmixed oxide contact material comprising:a) at least one cationic speciesof a naturally occurring Group IIIB element; b) at least one cationicspecies of a Group IIA metal selected from the group consisting ofmagnesium, calcium, strontium and barium; and c) at least one additionalmetal cationic species selected from the group consisting of germaniumand gallium;with said contacting being at oxidative coupling reactionconditions and in the presence of oxygen.
 2. The method of claim 1wherein the Group IIIB element is selected from the group consisting ofyttrium, lanthanum, neodymium, samarium and ytterbium.
 3. The method ofclaim 2 wherein the Group IIIB element is yttrium.
 4. The method ofclaim 1 wherein the Group IIA metal is barium.
 5. The method of claim 1wherein the additional metal is germanium.
 6. The method of claim 1wherein the additional metal is gallium.
 7. The method of claim 1wherein the contact material comprises the halogen chlorine.
 8. Themethod of claim 1 wherein the contact material comprises about 5 to 20wt. % of the halogen, on an elemental basis.
 9. The method of claim 1wherein the material comprises the cationic species of the Group IIIBelement, the Group IIA metal and the additional metal in an approximatemolar ratio of about 1 Group IIIB element to no more than about 3 of theGroup IIA metal, to no more than about 4 of the additional metal. 10.The method of claim 9 comprising a molar ratio of cationic species ofabout 1 mole of Group IIIB element to about 0.5-3 moles of the Group IIAmetal to about 0.5-4 moles of the additional metal.
 11. The method ofclaim 10 wherein the material comprises a molar ratio of cationicspecies of about 1 mole Group IIIB element to about 1.5-2.5 moles GroupIIA metal to about 0.5-1.5 moles additional metal.
 12. The method ofclaim 1 wherein the contact material has a surface area in the range ofabout 0.1 m² /g to about 100 m² /g.
 13. The method of claim 12 whereinthe contact material has a surface area in the range of about 1 m² /g toabout 10 m² /g.
 14. A method for converting lower alkanes to a productcomposition comprising a higher molecular weight hydrocarbon, saidmethod comprising contacting a feed composition comprising at least onelower alkane material with an intimately mixed alkaline earthhalide-containing mixed oxide contact material comprising an alkalineearth element selected from the group consisting of magnesium, calcium,strontium and barium and a halogen selected from the group consisting offluorine and chlorine, the contact material also comprising:a) at leastone cationic species of a naturally occurring Group IIIB elementselected from the group consisting of yttrium, lanthanum, neodymium,samarium and ytterbium, and b) at least one additional metal cationicspecies selected from the group consisting of germanium and gallium;with said contacting being at oxidative coupling reaction conditions andin the presence of oxygen.
 15. The method of claim 14 wherein the GroupIIIB element is yttrium.
 16. The method of claim 14 wherein the alkalineearth element is barium.
 17. The method of claim 14 wherein theadditional metal is germanium.
 18. The method of claim 14 wherein theadditional metal is gallium.
 19. The method of claim 14 wherein thealkaline earth halide is a chloride.
 20. The method of claim 14 whereinthe contact material comprises the cationic species in an approximatemolar ratio of about 1 mole Group IIIB element to about 0.5-3 molesGroup IIA element to about 0.5-4 moles additional metal.
 21. A methodfor converting methane to a product composition comprising a highermolecular weight hydrocarbon, said method comprising contacting a feedcomposition comprising methane with an intimately mixed bariumchloride-containing mixed oxide contact material of:a) a cationicspecies of yttrium, and b) a cationic species of germanium, with thecontacting being at oxidative coupling reaction conditions and in thepresence of oxygen.
 22. The method of claim 21 wherein the contactmaterial contains about 5 to 20 wt. % of chlorine, on an elementalbasis.
 23. The method of claim 21 wherein the contact materialcomprises, in an approximate molar ratio, about 1 mole yttrium to about0.5-3 moles barium to about 0.5-4 moles germanium.
 24. The method ofclaim 23 wherein the contact material comprises, on an approximate molarratio, about 1 mole yttrium to about 1.5-2.5 moles barium to about0.5-1.5 moles germanium.
 25. The method of claim 21 wherein the contactmaterial has a surface area in the range of about 1 m² /g to about 10 m²/g.
 26. A composition comprising an intimately mixed halogen-containingmixed oxide of:a) at least one cationic species of a naturally occurringGroup IIIB element; b) at least one cationic species of a Group IIAmetal selected from the group consisting of magnesium, calcium,strontium and barium; and c) at least one additional metal cationicspecies selected from the group consisting of germanium and gallium.